This invention relates to sweetening agents which may be employed as sugar substitutes in a wide variety of food, beverage, and confectionary products.
Various dihydrochalcones and their organic derivatives have been proposed in the prior art as sugar substitutes and sweeteners. In U.S. Pat. No. 3,087,821 there are disclosed various compounds having a high degree of individual sweetness, such as neohesperidin dihydrochalcone, naringin dihydrochalcone, and prunin dihydrochalcone. These compounds are prepared by known methods from the corresponding flavanone glycosides, such as neohesperidin, naringin, prunin and the like, which occur naturally in citrus and other fruits, and which may be recovered as a by-product of the fruit processing operations.
In the preparation of the respective dihydrochalcones, the flavanone glycosides are dissolved in strong caustic alkalies, such as sodium or potassium hydroxide solutions, such solutions having concentrations of the order of 10% to 25% by weight. The action of the alkali is to convert the flavanone glycoside to the corresponding chalcone. The alkali-solubilized flavanone glycoside is then transferred rapidly to an acid environment and subjected to strong acid hydrolysis to avoid separation of the flavanone glycoside, and to permit formation of the chalcone. Then the chalcone is catalytically reduced with hydrogen to form the dihydrochalcone derivative.
Various processes for the preparation of dihydrochalcone derivatives which follow the foregoing basic principles are additionally described in U.S. Pat. Nos. 2,700,047; 3,375,242; 3,364,196; 3,429,873; and 3,522,236. U.S. Pat. NO. 3,429,873 discloses the preparation of hesperitin dihydrochalcone glucoside, a compound of intense sweetness, from the starting material hesperidin which is itself tasteless. U.S. Pat. No. 3,522,236 describes a propoxy ether of a neohesperidin type dihydrochalcone which also possesses a high level of sweetness.
In all the processes described in the foregoing patents, there is formed, as a result of the initial alkali treatment, a water soluble alkali salt of the corresponding chalcone, by reaction of the phenolic hydroxyl groups in the flavanone nucleus. When this alkali salt is acidified, the free chalcone is obtained, which is then hydrogenated to the dihydrochalcone. Thus, at no time is there any formation of an alkali salt of the dihydrochalcone product. Moreover, the high concentration of alkali employed, ranging from 10% to 25%, which corresponds to 3 or 4 moles of alkali per mole of flavanone, insures that all of the available hydroxyl groups present are neutralized. The art has recognized, moreover, that the use of less than this molar ratio, for example, 2 moles of alkali, was insufficient to form the desired chalcone. The maintenance of a sufficiently high molar ratio of alkali to flavanone to effect chalconization is described in U.S. Pat. No. 2,700,047, which indicates that to completely chalconize hesperidin, the requisite ratio of alkali to hesperidin would be about 3 moles alkali to 1 mole hesperidin. However, as pointed out above, no alkali treatment of the final dihydrochalcone compounds themselves is disclosed or contemplated, nor any salts of those dihydrochalcones which were known to be sweet when in their nonionic forms.